Together, they were also famous early mountain-climbers. They made ascents of peaks in the Himalayas of over 18,000 feet. In 1906, they were the first to reach the summit of Nun Kun's Pinnacle Peak - 22,736 feet.

Co-authors of books on their travels: - "Algerian Memories: A Bicycle Tour over the Atlas to the Sahara", 1895 - "Sketches Awheel in Modern Iberia", 1897 - "In the Ice World of Himalaya", 1900 - "Through Town and Jungle: Fourteen Thousand Miles A-Wheel Among the Temples and People of the Indian Plain", 1904 - "Ice-Bound Heights of the Mustagh", 1908 - "Peaks and Glaciers of Nun Kun", 1909 - "The Call of the Snowy Hispar", 1910 - "Two Summers in the Ice Wilds of Eastern Karakoram", 1917